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Since his return to Earth, the astronaut has shared photos of life on the ground

(CNN)Well, that didn't last long.

Astronaut Scott Kelly, who grew about 2 inches during his nearly one year stay on the International Space Station, is back to his normal height, his identical twin brother, Mark, said Thursday.

Scott Kelly, whose spine elongated while he spent 340 days in space, took less than two days to shrink.

Mark Kelly, a former astronaut, told CNN's "Erin Burnett OutFront" by email that the two went back-to-back an hour after his brother returned to the United States early Thursday.

Scott grew 1½ inches before returning to normal, he said.

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Scott Kelly landed in Kazakhstan on Wednesday morning, and arrived in Houston to hugs and American treats a day later.

There he was welcomed by his twin, second lady Jill Biden and various NASA officials.

Biden brought the astronaut some beer and apple pie.

"Nothing's more American than that," she said. "... That's what he said he wanted."

'It's great to be back'

Scott Kelly, 52, attributed the success of his year in space to his NASA colleagues, family and friends.

"It's great to be back in Texas, on U.S. soil ... on planet Earth," he said.

"This is not my achievement. It's NASA's achievement and it's our country's achievement. ... There's no greater privilege than serving your country however and wherever you might do it."

In a phone call, President Barack Obama applauded him for his record-breaking yearlong mission.

In a statement, the White House said, "Kelly's year in space would provide critical data to researchers trying to understand how to keep astronauts healthy during long space voyages and fulfill the President's vision of putting American astronauts on Mars in the 2030s."

Pool plunge

Though he's no longer an astronaut, Mark Kelly volunteered to take part in NASA's "Twins Study" with his brother. NASA wants to see how the identical twins measure up after a year in two very different environments: Scott in space and Mark on Earth.

Scott Kelly returned to Earth after 340 days, the longest any U.S. astronaut has been in space.

Since then, he's been getting reacquainted with his planet. After garnering a million Twitter followers during his stint in space, the astronaut has started tweeting about life back on the ground -- including a long-awaited plunge into a swimming pool while still wearing his NASA jumpsuit.